Power Storage Device and Manufacturing Method Thereof

ABSTRACT

A power storage device having a small thickness is manufactured. A manufacturing method of the power storage device includes: forming a first layer and a second layer over a first substrate; forming a first insulating layer, a positive electrode and a negative electrode over the second layer; forming a solid electrolyte layer over the first insulating layer, the positive electrode, and the negative electrode; forming a sealing layer to cover the solid electrolyte layer; forming a planarization film and a support over the sealing layer; separating the first layer and the second layer from each other so that the second layer, the positive electrode, the negative electrode, the solid electrolyte layer, the sealing layer, the planarization film, and the support are separated from the first substrate; attaching the separated structure to a second substrate which is flexible; and separating the support from the planarization film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention disclosed in this specification relates to powerstorage devices.

2. Description of the Related Art

In recent years, power storage devices such as lithium-ion secondarybatteries where carbon or lithium metal oxide is used as a batterymaterial and which are charged and discharged by the movement of lithiumions as carrier ions between a positive electrode and a negativeelectrode, and electrochemical capacitors, have been actively developed(see Patent Documents 1 to 3).

Further, among such lithium-ion secondary batteries, all-solid-statelithium-ion secondary batteries in which a solid electrolyte is usedinstead of a liquid electrolyte have been developed (see PatentDocuments 4 to 6 and Non-Patent Document 1).

REFERENCES Patent Documents

-   [Patent Document 1] Japanese Published Patent Application No.    2008-294314-   [Patent Document 2] Japanese Published Patent Application No.    2002-289174-   [Patent Document 3] Japanese Published Patent Application No.    2007-299580-   [Patent Document 4] Japanese Published Patent Application No.    2004-158222-   [Patent Document 5] Japanese Published Patent Application No.    2006-185913-   [Patent Document 6] Japanese Published Patent Application No.    2007-134305

Non-Patent Document

-   [Non-Patent Document 1] Yoichiro Hata, “Development of integrated    production equipment for 50 μm thick, all-solid-state lithium-ion    batteries,” EE Times Japan, Jan. 21, 2009,    http://eetimes.jp/article/22693

SUMMARY OF THE INVENTION

In formation of an all-solid-state power storage device, the deviceshould be formed over a thick substrate such as a glass substrate or asilicon substrate. Such substrates are thick, and thus the power storagedevices formed over such substrates are also thick. Therefore, it is anobject of one embodiment of the present invention disclosed in thisspecification to reduce the thickness of a power storage device.

It is also an object of one embodiment of the present inventiondisclosed in this specification to reduce the size, thickness, andweight of an electric device which incorporates the power storagedevice.

After a power storage device is formed over a thick substrate such as aglass substrate or a silicon substrate, the power storage device isseparated from the substrate and the separated power storage device isattached to a flexible substrate. In this manner, a thin power storagedevice is manufactured.

One embodiment of the present invention is a power storage deviceincluding a positive electrode and a negative electrode over a flexiblesubstrate, the positive electrode including a positive-electrode currentcollecting layer and a positive-electrode active material layer over thepositive-electrode current collecting layer, and the negative electrodeincluding a negative-electrode current collecting layer and anegative-electrode active material layer over the negative-electrodecurrent collecting layer; a solid electrolyte layer over the substrate,the positive-electrode active material layer, and the negative-electrodeactive material layer; and a sealing layer covering thepositive-electrode active material layer, the negative-electrode activematerial layer, and the solid electrolyte layer.

One embodiment of the present invention is a method for manufacturing apower storage device, comprising the steps of: forming, over a firstsubstrate, a first layer and a second layer which have low adhesivenessto each other; forming a first insulating layer over the second layer;forming a positive-electrode current collecting layer and anegative-electrode current collecting layer over the first insulatinglayer; forming a positive-electrode active material layer and anegative-electrode active material layer over the positive-electrodecurrent collecting layer and the negative-electrode current collectinglayer, respectively, wherein the positive-electrode current collectinglayer and the positive-electrode active material layer serve as apositive electrode, and the negative-electrode current collecting layerand the negative-electrode active material layer serve as a negativeelectrode; forming a solid electrolyte layer over the first insulatinglayer, the positive electrode, and the negative electrode; forming asealing layer to cover the solid electrolyte layer; forming aplanarization film and a support over the sealing layer; separating thefirst layer and the second layer from each other so that the secondlayer, the positive electrode, the negative electrode, the solidelectrolyte layer, the sealing layer, the planarization film, and thesupport are separated from the first substrate; attaching the secondlayer, the positive electrode, the negative electrode, the solidelectrolyte layer, the sealing layer, the planarization film, and thesupport which have been separated from the first substrate to a secondsubstrate which is flexible; and separating the support from theplanarization film.

According to one embodiment of the present invention disclosed in thisspecification, a power storage device having a small thickness can bemanufactured. Further, by incorporating such a power storage devicehaving a small thickness, a miniaturized electric device can bemanufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1E are cross-sectional views of a manufacturing process of apower storage device;

FIGS. 2A to 2C are cross-sectional views of a manufacturing process of apower storage device; and

FIG. 3 is a top view of a manufacturing process of a power storagedevice.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention disclosed in this specificationwill be hereinafter described with reference to the accompanyingdrawings. Note that the present invention disclosed in thisspecification can be carried out in a variety of different modes, and itis easily understood by those skilled in the art that the modes anddetails of the present invention disclosed in this specification can bechanged in various ways without departing from the spirit and scopethereof. Therefore, the present invention disclosed in thisspecification should not be interpreted as being limited to thedescription in the embodiments. Note that in the accompanying drawings,the same portions or portions having similar functions are denoted bythe same reference numerals, and repetitive description thereof isomitted.

Embodiment 1

This embodiment will be described with reference to FIGS. 1A to 1E,FIGS. 2A to 2C, and FIG. 3.

First, a first layer 102 and a second layer 103 which have lowadhesiveness to each other are formed over a substrate 101 (FIG. 1A).

The substrate 101 can be a glass substrate, a quartz substrate, aplastic substrate, or the like having an insulating surface.Additionally, a conductive substrate of metal or the like or a substratein which an insulating film is formed over a semiconductor substrate ofsilicon or the like can be used.

At the interface between the first layer 102 and the second layer 103which have low adhesiveness to each other, the first layer 102 and thesecond layer 103 can be separated from each other, so that the substrate101 and the first layer 102 can be separated from a stacked structureformed over the second layer 103.

Examples of the combination of the first layer 102 and the second layer103 which have low adhesiveness to each other include a combination of ametal film and a silicon oxide film, and the like. Specifically, atungsten film may be formed as the first layer 102 and a silicon oxidefilm or the like may be formed over the first layer 102 by a sputteringmethod as the second layer 103.

In addition, the first layer 102 and the second layer 103 do notnecessarily need to originally have low adhesiveness to each other, anda combination of films whose adhesiveness can be lowered by a certainprocess after formation of the films may be used. For example, anamorphous silicon film as the first layer 102 and a silicon oxide filmas the second layer 103 are stacked, the formed films are subjected toheating or laser irradiation from the rear face side of the substrate101, so that the amorphous silicon film is crystallized to lower theadhesiveness between the first layer 102 and the second layer 103.

Then, an insulating layer 114 is formed over the second layer 103. Apositive-electrode current collecting layer 104 and a negative-electrodecurrent collecting layer 106 are formed over the insulating layer 114(FIG. 1B).

In this embodiment, the positive-electrode current collecting layer 104and the negative-electrode current collecting layer 106 are each formedusing a metal film of platinum (Pt), titanium (Ti), aluminum (Al),copper (Cu), gold (Au), or the like by a sputtering method.

A positive-electrode active material layer 105 is formed over thepositive-electrode current collecting layer 104 and a negative-electrodeactive material layer 107 is formed over the negative-electrode currentcollecting layer 106 (FIG. 1C). The positive-electrode currentcollecting layer 104 and the positive-electrode active material layer105 are referred to as a positive electrode 121, while thenegative-electrode current collecting layer 106 and thenegative-electrode active material layer 107 are referred to as anegative electrode 122. In this embodiment, as each of thepositive-electrode active material layer 105 and the negative-electrodeactive material layer 107, a film of carbon (C) is formed by asputtering method. Graphite can be given as an example of carbon (C).

The positive-electrode active material layer 105 may be formed using alithium-containing composite oxide represented by a chemical formulaLi_(x)M_(y)O₂ (wherein M represents Co, Ni, Mn, V, Fe, or Ti, and x isin the range of from 0.2 to 2.5 and y is in the range of from 0.8 to1.25), such as LiCoO₂ or LiNiO₂. Note that in the case where theaforementioned lithium-containing composite oxide represented by thechemical formula Li_(x)M_(y)O₂ is used for the positive-electrode activematerial layer 105 of a lithium-ion secondary battery, M may includeeither one element or two or more elements. In other words, for thepositive-electrode active material layer 105 of a lithium-ion secondarybattery, a multi-element, lithium-containing composite oxide may beused.

Furthermore, for the positive-electrode active material layer 105, ametal compound (oxide, sulfide, or nitride) having a layered structurecan be used.

In the case where a lithium-containing composite oxide represented byLi_(x)M_(y)O₂ or a metal compound having a layered structure is used forthe positive-electrode active material layer 105, a power storage deviceof this embodiment functions as a secondary battery.

Next, in the case where a capacitor is manufactured as a power storagedevice, the carbon film which is formed as the positive-electrode activematerial layer 105 is processed into activated carbon by steamactivation or alkali activation.

In addition, in the case where a capacitor is manufactured as a powerstorage device, a lithium film 115 is formed over the negative-electrodeactive material layer 107, whereby lithium ions of the lithium film 115are added to the negative-electrode active material layer 107 so thatthe negative-electrode active material layer 107 is doped with thelithium ions. By doping the negative-electrode active material layer 107with lithium ions, lithium ions serving as carrier ions can beintroduced in advance, and a larger number of ions can be used ascarrier ions.

The carrier ions are not limited to lithium ions and may be other alkalimetal ions or alkaline earth metal ions. The other alkali metal ions maybe sodium (Na) ions, and the alkaline earth metal ions may be magnesium(Mg) ions or calcium (Ca) ions.

In order to introduce the other alkali metal ions or alkaline earthmetal ions into the negative-electrode active material layer 107 ascarrier ions in the above manner, a film for ions serving as carrierions may be formed over the negative-electrode active material layer107, whereby the ions in the formed film may be added to thenegative-electrode active material layer 107 so that thenegative-electrode active material layer 107 is doped with the ions, asin the case of lithium ions.

Next, a solid electrolyte layer 108 is formed between the positiveelectrode 121 and the negative electrode 122 (FIG. 1D).

In this embodiment, sputtering of lithium phosphate (Li₃PO₄) isconducted in a nitrogen atmosphere to form a film of lithium phosphorousoxynitride (LiPON) having a thickness of about 1.0 μm as the solidelectrolyte layer 108. Alternatively, lithium hexafluorophosphate(LiPF₆), lithium fluoroborate (LiBF₄), or the like may be used insteadof lithium phosphate.

The solid electrolyte layer 108 should not be damaged by plasma duringthe film formation by sputtering.

The solid electrolyte layer 108 may be amorphous or crystalline.Furthermore, for the solid electrolyte layer, a polymer electrolyte or agel electrolyte may be used.

A sealing layer 109 is formed to cover the positive electrode 121, thenegative electrode 122, and the solid electrolyte layer 108 (FIG. 1E).The sealing layer 109 is preferably formed using a material whichcontains no oxygen. In addition, moisture or oxygen should be preventedfrom entering the sealing layer 109. As the sealing layer 109, forexample, a polyurea resin film may be used.

Next, a planarization film 111 is formed over the sealing layer 109, anda support 112 is formed over the planarization film 111 (FIG. 2A). Inthis embodiment, as the planarization film 111, an organic resin such asan epoxy resin or a structure in which a fibrous body is impregnatedwith an organic resin (also referred to as a “prepreg”) is used.

The support 112 can be a substrate to which a thermoplastic resin or aphotoplastic resin is applied as an adhesive. In addition, the support112 itself is also preferably a flexible substrate, in which case apower storage device or the like is not damaged when separated from thesubstrate.

Then, the positive electrode 121, the negative electrode 122, the solidelectrolyte layer 108, the sealing layer 109, the planarization film111, and the support 112 are separated from the substrate 101 (FIG. 2A).Note that the separation is brought in the interface between the firstlayer 102 and the second layer 103 which have low adhesiveness to eachother.

The positive electrode 121, the negative electrode 122, the solidelectrolyte layer 108, the sealing layer 109, the planarization film111, and the support 112 which have been separated from the substrate101 are attached to a flexible substrate 113. Then, the support 112 isseparated from the planarization film 111 (FIG. 2C). Through the abovemanufacturing process, the power storage device is manufactured over theflexible substrate 113.

FIG. 3 is a top view of the power storage device over the flexiblesubstrate 113. The positive-electrode current collecting layer 104 andthe negative-electrode current collecting layer 106 extend outside thesealing layer 109. The extending portions of the positive-electrodecurrent collecting layer 104 and the negative-electrode currentcollecting layer 106 may each be electrically connected to an externalterminal. In addition, the cross-sectional view taken along the lineA-A′ in FIG. 3 is FIG. 2C.

In one embodiment of the present invention disclosed in thisspecification, after a power storage device is formed over a thicksubstrate, the power storage device is separated from the substrate andthe separated power storage device is attached to a thin substrate, asdescribed above. In this manner, a power storage device having a smallthickness can be manufactured.

This application is based on Japanese Patent Application serial no.2009-069179 filed with Japan Patent Office on Mar. 20, 2009, the entirecontents of which are hereby incorporated by reference.

1. A power storage device comprising: a flexible substrate; a positiveelectrode over the flexible substrate, the positive electrode including:a positive-electrode current collecting layer; and a positive-electrodeactive material layer over the positive-electrode current collectinglayer; a negative electrode over the flexible substrate, the negativeelectrode including: a negative-electrode current collecting layer; anda negative-electrode active material layer over the negative-electrodecurrent collecting layer; a solid electrolyte layer over the flexiblesubstrate, the positive-electrode active material layer, and thenegative-electrode active material layer; and a sealing layer coveringthe positive-electrode active material layer, the negative-electrodeactive material layer, and the solid electrolyte layer.
 2. The powerstorage device according to claim 1, wherein the power storage device isan all-solid-state power storage device.
 3. The power storage deviceaccording to claim 1, wherein the positive-electrode current collectinglayer comprises a material selected from the group consisting ofplatinum (Pt), titanium (Ti), aluminum (Al), copper (Cu), and gold (Au).4. The power storage device according to claim 1, wherein thenegative-electrode current collecting layer comprises a materialselected from the group consisting of platinum (Pt), titanium (Ti),aluminum (Al), copper (Cu), and gold (Au).
 5. A method for manufacturinga power storage device, comprising the steps of: forming, a first layerover a first substrate; forming, a second layer over the first layer;forming a first insulating layer over the second layer; forming apositive-electrode current collecting layer and a negative-electrodecurrent collecting layer over the first insulating layer; forming apositive-electrode active material layer and a negative-electrode activematerial layer over the positive-electrode current collecting layer andthe negative-electrode current collecting layer, respectively, whereinthe positive-electrode current collecting layer and thepositive-electrode active material layer serve as a positive electrode,and the negative-electrode current collecting layer and thenegative-electrode active material layer serve as a negative electrode;forming a solid electrolyte layer over the first insulating layer, thepositive electrode, and the negative electrode; forming a sealing layerto cover the solid electrolyte layer; forming a planarization film and asupport over the sealing layer; separating the first layer and thesecond layer from each other so that the second layer, the positiveelectrode, the negative electrode, the solid electrolyte layer, thesealing layer, the planarization film, and the support are separatedfrom the first substrate; attaching the second layer, the positiveelectrode, the negative electrode, the solid electrolyte layer, thesealing layer, the planarization film, and the support to a secondsubstrate which is flexible; and separating the support from theplanarization film.
 6. The power storage device according to claim 5,wherein the power storage device is an all-solid-state power storagedevice.
 7. The power storage device according to claim 5, wherein thepositive-electrode current collecting layer comprises a materialselected from the group consisting of platinum (Pt), titanium (Ti),aluminum (Al), copper (Cu), and gold (Au).
 8. The power storage deviceaccording to claim 5, wherein the negative-electrode current collectinglayer comprises a material selected from the group consisting ofplatinum (Pt), titanium (Ti), aluminum (Al), copper (Cu), and gold (Au).9. The power storage device according to claim 5, wherein the firstlayer and the second layer have low adhesiveness to each other, andwherein a combination of the first layer and the second layer is acombination of a metal film and a silicon oxide film.
 10. The powerstorage device according to claim 5, wherein the planarization film isan organic resin.
 11. The power storage device according to claim 5,wherein the planarization film is a structure in which a fibrous body isimpregnated with an organic resin.
 12. A method for manufacturing apower storage device, comprising the steps of: forming, a first layerover a first substrate; forming, a second layer over the first layer;forming a first insulating layer over the second layer; forming apositive electrode and a negative electrode over the first insulatinglayer; forming a solid electrolyte layer over the first insulatinglayer, the positive electrode, and the negative electrode; forming asealing layer to cover the solid electrolyte layer; forming aplanarization film and a support over the sealing layer; separating thefirst layer and the second layer from each other so that the secondlayer, the positive electrode, the negative electrode, the solidelectrolyte layer, the sealing layer, the planarization film, and thesupport are separated from the first substrate; attaching the secondlayer, the positive electrode, the negative electrode, the solidelectrolyte layer, the sealing layer, the planarization film, and thesupport to a second substrate which is flexible; and separating thesupport from the planarization film.
 13. The power storage deviceaccording to claim 12, wherein the power storage device is anall-solid-state power storage device.
 14. The power storage deviceaccording to claim 12, wherein the first layer and the second layer havelow adhesiveness to each other, and wherein a combination of the firstlayer and the second layer is a combination of a metal film and asilicon oxide film.
 15. The power storage device according to claim 12,wherein the planarization film is an organic resin.
 16. The powerstorage device according to claim 12, wherein the planarization film isa structure in which a fibrous body is impregnated with an organicresin.